Variable valve actuating apparatus

ABSTRACT

An actuating apparatus, which can be used to perform variable valve timing of the intake or exhaust valves of an internal combustion engine, includes a hollow shaft with at least one slot defined through a cylindrical wall. A movable cam member is disposed to project through the slot and is rotatable relative to the hollow shaft in a channel defined in the interior surface of the hollow shaft. A base circle band extends circumferentially around the outer surface of the hollow shaft between the endwalls of the slot. The exterior surface of the hollow shaft can define grooves which receive front or back ear members of the cam member. The exterior surface of the hollow shaft also can define recesses, which in some embodiments have bottom surfaces and in other embodiments have partial bottom surfaces or no bottom surface. The recesses can receive tongue members formed on the cam member. The cam member can be engaged by a cam follower that has a roller to engage the cam surface. When the length of the roller exceeds the width of the cam surface, base circle arcuate sections can be provided on the exterior surface of the hollow shaft to carry the roller across the exposed portion of the slot that exists between the endwall of the slot and the free end of the cam member. An inner shaft extends through an opening defined transversely through the cam member and nonrotatably engages same. The nose portion of the cam member can be defined by a rotatable roller. Twin cam members having identical cam surface profiles can be disposed side-by-side, with one cam member projecting through the slot and the other cam member secured to the outer surface of the hollow shaft. A single follower such as a tappet defining a circular cylindrical surface can be provided to engage both cam members and can be held nonrotatably.

This is a continuation of application Ser. No. 07,943,755, filed Sep.10, 1992, which was abandoned upon the filing hereof and which is adivisional application of Ser. No. 07/827,618, filed Jan. 29, 1992, nowU.S. Pat. No. 5,161,429, which is a division of 07/530,546, filed May29, 1990, now U.S. Pat. No. 5,136,887.

BACKGROUND OF THE INVENTION

The present invention relates to variable cam apparatus primarily forimplementing variable valve timing techniques in internal combustionengines, and more particularly to such apparatus employing rollers.

Mechanisms using a camshaft capable of varying the timing of valves,i.e., when the valves open and when the valves close, in relation to themovement of the crankshaft, and how long they remain open or closed, areknown. In some devices, variable timing is obtained by controlling thecam follower geometry. U.S. Pat. No. 4,357,917 to Aoyama discloses anumber of different geometries for the nose portion of a cam (FIGS. 9A,9B, and 9C) used in a variable valve timing system for induction controlof an internal combustion engine.

In a number of the variable valve timing mechanisms, a cam lobe ismovable relative to the outer cylindrical surface of the camshaft. Suchdesigns include U.S. Pat. No. 4,770,060 to Elrod et al. U.S. Pat. No.4,771,742 to Nelson et al, and U.S. Pat. No. 4,917,058 to Nelson et al.which patents are hereby incorporated herein by reference. In many ofthese movable lobe camshafts, the cam follower is a flat surfacedisposed at the end of a valve tappet. Examples of this design shown inU.S. Pat. No. 2,888,837 to Hellmann, DE 3,234,640A to Kruger. DE2,921,645 to Lehr, French Patent No. 1,109,790 to Rooy. Patentschrift704,575 to Von Ruti, and U.S. Pat. No. 1,527,456 to Woydt et al. Analternative design uses followers with a curved surface. Examples ofcurved follower surfaces are shown in DE 3212-663-A to Martin (FIG. 1),U.S. Pat. No. 4,388,897 to Rosa (FIG. 7), and U.S. Pat. No. 4,770,060 toElrod et al (FIG. 3). In some such curved follower designs, DE 3212-663-A to Martin for example, the base of the cam rides above the outercylindrical surface of the camshaft and meets the circular surfacetangentially and continuously so that a follower encounters little or nodiscontinuity upon leaving the cam surface and engaging the camshaftsurface where the cam surface ends.

As known in the art, the reduction of friction in the valve train canresult in more efficient engine output. The use of roller followers canreduce friction where the cam surface meets the follower surface. In afurther alternative design, roller followers are used to engage thesurface of a movable cam. Examples of the roller follower designsinclude a multi-linkage design shown in the top center FIG. 10 of anarticle entitled "Variable Valve Timing for IC Engines" appearing inVolume 10, No. 4, of Automotive Engineer (August-September 1983), andthe more conventional designs shown in Patentschrift 727,987 to Borner.U.S. Pat. No. 862,448 to Cornilleau. and U.S. Pat. No. 733,220 to Krebs.In contrast to the designs employing flat or curved surfaces as camfollowers, the devices employing roller followers encounter distinctproblems relating to rising and falling movements of the rollerfollowers over short durations. These roller follower movementstranslate through a suitable linkage to corresponding sudden, briefopening and closing movements of the valves. These valve movementsinterrupt the rate at which the valve is opening or closing, as the casemay be. Such movements either briefly accelerate the trend (opening orclosing) of valve movement or decelerate the trend of valve movement.One of these problems occurs when the roller moves between thecamshaft's base circle, which is defined by the exterior surface of thecamshaft, and either the beginning of the leading edge of the camsurface or the end of the trailing edge of the cam surface.

The problem relating to the base of the cam is illustrated well in U.S.Pat. No. 862,448 to Cornilleau, which uses a roller follower to engage acam lobe which moves in a radial direction into and out of a slot in thecamshaft. As shown in particular in Cornilleau FIGS. 13, 15 and 16, theroller encounters a gap between the riding surface of the cam and theriding surface on the exterior surface of the camshaft.

The problem is also apparent in Patentshrift No. 727,987 to Borner. AU-shaped main cam is fixed to rotate with the Borner shaft, and asecondary cam is connected to a solid shaft inside the hollow main shaftand projects through an opening in the main shaft corresponding to anopening in the U-shaped portion of the main cam. The secondary cam ismovable into and out of this opening in the U-shaped portion of the cam.In this way, one can change the length of the cam surface which opensthe valve and maintains the valve in the open position. This permitschanging the duration of time during which the valve is held open forexample. The roller is initially lifted on the full width of the maincam so that during the lifting of the valve, the entire inertia of thecontrol mechanism as well as the tension of the valve springs and thegas pressure against the valve head can be spread over the full width,which thus is available to absorb the forces without an unduly highsurface pressure. The linkage roller rolls first of all over the upperhead of the main cam. Then the linkage roller moves over the preciselyequally high head of the secondary cam. Finally, the linkage rollerdrops suddenly as it moves over the closing ramp and onto the lower camsurface whereby the valve closes. The failure of the surfaces to match,produces discontinuous roller motion when the linkage roller drops uponthe closing ramp onto the lower cam surface. Thus, the otherwise smoothrising and falling motion of the rollers, which translates through asuitable linkage to activate valves for example, becomes subject tosudden discontinuous movements as the roller rides on the transitionportions of the cam surface.

Instead of a U-shaped design, Borner's main cam can be designed in asplit fashion whereby both halves of both sides can be pushed over thesecondary cam. However, this split design does not alleviate the problemjust described.

Devices shown in documents DE 3234640A1 to Kruger. DE 2921645A to Lehr,and DE 3212663A1 to Martin, which involve movable cams engaging flatsurface followers or curved surface followers, are affected far lessthan roller followers when engaged by movable cams.

The Martin movable cam 3 has extended ears which overlap and ride on orabove an inner sleeve that is integral with the camshaft and thenonmovable cam. The movable cam 3 is keyed to rotate with inner shaftelement 2. The valve tappet 4 has a curved follower surface in the shapeof a partial circle whose radius corresponds to the elevation of the camfrom the axis of the shaft. The follower surface engages the movable camat a single point, similar to the roller follower. However, when thetransition from the movable cam to the base circle of the camshaft mustbe bridged, the curved surface of the follower engages the movable camat one point and the base circle of the camshaft at another point. Bycontrast, the roller follower is incapable of engaging the movable camat one point and the base circle at another point without riding up anddown the valley formed between the base circle and the movable cam.However, as noted above, it becomes desirable if roller followers can beused. Moreover, in such environments, variable valve timing mechanismsemploying a movable cam lobe also are desirable.

OBJECTS AND SUMMARY OF THE INVENTION

It is a principal object of the present invention to reduce the level offriction in a cyclical actuating apparatus employing one or more cams,without introducing discontinuous movements during the actuating motionof an individual actuation cycle.

Another principal object of the present invention is to provide acyclical actuating apparatus for the valves of an internal combustionengine, wherein the apparatus has variable valve capability, providesrelatively reduced levels of friction in the valve train, andaccomplishes the foregoing without introducing discontinuous valvemovements during an individual engine cycle.

Additional objects and advantages of the invention will be set forth inpart in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and attained bymeans of the instrumentalities and combinations particularly pointed outin the appended claims.

To achieve the objects and in accordance with the purpose of theinvention, as embodied and broadly described herein, the actuatingapparatus of the present invention is designed so that it can be used aspart of the mechanism which actuates the opening and closing of valves(both intake and exhaust) in internal combustion engines (both sparkignition and diesel).

In accordance with the present invention, an elongated hollow shaft isprovided. The hollow shaft preferably defines a longitudinal axis, anexterior surface, an interior surface, and a slot defined through theinterior and exterior surfaces. Portions of the interior surface definea circular cylindrical shaped bearing surface that can be used torotatably support a solid inner shaft (described hereafter) as well asother members (also described hereafter). The slot is defined with apair of opposed sidewalls and a pair of opposed endwalls disposedbetween the sidewalls. Preferably, the slot sidewalls are continuous,and the slot endwalls can be either continuous or discontinuous. Aseparate slot will be defined through the cylindrical wall of the hollowshaft so that one slot is available for each movable cam member(described hereafter) that is desired as part of the actuating apparatusof the present invention. Thus, typically, the hollow shaft will beprovided with several slots arranged at different locations along thelength of the hollow shaft.

In further accordance with the present invention, the exterior surfaceof the hollow shaft defines a base circle band, which is a portion ofthe exterior surface of the hollow shaft that extends between theendwalls of each slot. The base circle band extends in the longitudinaldirection of the hollow shaft, beyond the portion defined between thesidewalls of the slot. The base circle band is defined by a constantradius of curvature and is intended to carry the cam follower when thefollower leaves the surface of the cam.

In those embodiments of the present invention designed to be used withcam followers that are longer than the width of the cam surface, thehollow shaft further can define base circle arcuate sections. These basecircle arcuate sections provide upper cam receding surfaces. These uppercam receiving surfaces have the same radius of curvature as the basecircle band and are disposed so as to be able to carry the peripheraledges of the cam follower, especially a roller follower. The base circlearcuate sections preferably are disposed beside the sidewalls and nearthe vicinity of where the sidewalls meet the endwalls of the slot. Theupper cam receiving surfaces of the base circle arcuate sections carrythe roller follower over the gap that can be produced between theendwall of the slot and the free edge of the movable cam member(described hereafter) that is configured to meet the endwall of theslot. Each base circle arcuate section has a minimum length that is longenough to extend the full arcuate distance that the slot is exposed whenthe movable cam member is oriented for maximum exposure of the slotbetween the slot endwall and the surface of the movable cam member thatis configured to abut with the slot endwall. Moreover, the two basecircle arcuate sections disposed to one side of the slot can be formedintegrally with one another and integrally with the periphery of thebase circle band. In other words, the combination of the periphery ofthe base circle band and the two base circle arcuate sections on oneside of the slot can extend around the full 360 of the hollow shaft andform a base circle ring with a continuous upper cam receiving surfacethat can carry the free end of the roller of a roller follower.

In still further accordance with the present invention, the hollow shaftis provided with a channel that is defined in the interior cylindricalbearing surface of the hollow shaft. The channel has channel sidewallsand a channel bearing surface. Instead of having channel endwalls, thechannel begins and ends where the slot begins and ends. The channelbearing surface is disposed generally opposite to the slot definedthrough the hollow shaft. The channel bearing surface is configured torotatably support the movable cam member to enable the movable cammember to rotate relative to the hollow shaft. Thus, the channelsidewalls are generally disposed parallel to the slot sidewalls.Preferably, the channel is formed on the opposite surface of the hollowshaft on which the base circle band is formed. In this construction, anadditional thickness of material is afforded at the location of thehollow shaft where the channel is disposed and the movable cam member isto be supported by the channel bearing surface defined in the hollowshaft. Preferably, the joints where the channel bearing surface meetsthe channel sidewalls are filleted to avoid stress concentrations.

In still further accordance with the present invention, a movable cammember is provided and defines an actuating lobe and a seating member.Preferably, the actuating lobe and the seating member are integrallyconnected to each other and typically will be manufactured as theopposite ends of a unitary movable cam member. The seating member has anouter circular cylindrical shaft bearing surface that can rotatablyengage the channel bearing surface of the interior surface of the hollowshaft. The actuating lobe defines a cam surface that is configured to beable to project through the slot from inside the hollow shaft. When theactuating lobe projects through the slot, the outer cylindrical shaftbearing surface will be disposed to rotatably engage the channel bearingsurface. The cam surface is configured to engage the cam follower in amanner that raises and lowers the follower according to a desiredpattern of actuating the valve, which is connected to the follower bymechanical or other means. The cam surface defines a nose ramp (locatedat the nose portion of the cam member), a leading ramp, and a trailingramp. The nose ramp is situated between the leading ramp and thetrailing ramp and is disposed the greatest distance away from the outercylindrical shaft bearing surface of the seating member. The leadingramp forms the portion of the cam surface that is engaged by the camfollower before the cam follower engages the nose ramp. Similarly, thetrailing ramp forms that portion of the cam surface that engages the camfollower after the cam follower rides over the nose ramp duringrevolution of the hollow shaft.

In yet further accordance with the present invention, an elongated innershaft is provided. The elongated inner shaft defines a longitudinal axisof rotation.

In still further accordance with the present invention, means areprovided for nonrotatably connecting the inner shaft and the movable cammember for simultaneous rotational movement. In one embodiment of thenonrotatable connecting means, two mating sets of radially extendingspline members are provided. One set is provided on the outer surface ofthe inner shaft, and a second set is provided on the internalcircumference of an opening formed transversely through the movable cammember in the vicinity of the outer cylindrical shaft bearing surface.The spline members interlock with one another and prevent relativerotation between the inner shaft and the movable cam member. Anotherembodiment of the nonrotatable connecting means provides the inner shaftwith a non-circular cross-section and a bushing surrounding the innershaft with a non-circular opening that mates with the cross-section ofthe inner shaft. Still another embodiment of the nonrotatable connectingmeans employs a shrink-fitting technique. In yet a further embodiment ofthe nonrotatable connecting means, a raised key member is disposed toextend from the perimeter of the opening defined through the movable cammember. The key member extends in a direction opposite to the nose rampand toward the center of the opening defined through the movable cammember. A key recess is then defined in the outer surface of the innershaft along the length thereof to the point where the movable cam memberis to be located circumferentially and longitudinally with respect tothe outer surface of the inner shaft. The shrink-fit embodiment and thekey embodiment permit a greater thickness of material forming theseating member, and this adds to the strength of the cam member and itsability to bear the stresses which are placed on the movable cam memberduring operation of the apparatus.

The movable cam member can define a front stop surface and a back stopsurface. These surfaces form the portion of the movable cam member thatbutts against the endwalls of the slot. They can extend from the freeend of the leading ramp and the trailing ramp, respectively.

In some embodiments of the present invention, the exterior surface ofthe hollow shaft can define a pair of grooves. One end of each groovecan be connected to one of the two opposite ends of the slot andintersect with or replace the endwall of the slot, while the other endof each groove can be formed by a groove endwall. Each groove has abottom surface that defines an exterior cylindrical ear bearing surfacethat is used to support a corresponding surface formed in the movablecam member associated with this particular embodiment of the hollowshaft. This associated embodiment of the movable cam member defines afront ear and a back ear. The exterior surface of the front ear extendsfrom the end of the leading ramp that is disposed opposite from the noseramp. At least a portion of the exterior surface of the front ear thatis in the vicinity of the free end of the front ear is defined by thesame radius of curvature that defines the base circle band of the hollowshaft. The front ear and the back ear each further define an innercylindrical ear bearing surface that is disposed opposite the exteriorsurface of the front ear and back ear, respectively. The innercylindrical ear bearing surface defines the same constant radius ofcurvature that defines the exterior cylindrical ear bearing surface ofthe grooves of the hollow shaft. The inner cylindrical ear bearingsurface and the outer cylindrical shaft bearing surface define theboundary of ear cavities which can receive a portion of the hollow shaftslidably into and out of the cavity as the movable cam member rotatesits outer cylindrical shaft bearing surface relative to the channelbearing surface of the interior surface of the hollow shaft. Theseembodiments of the movable cam member permit the hollow shaft to beformed of added material in the portion of the hollow shaft that isreceivable inside the ear cavities. This added material strengthens thehollow shaft in the vicinity of the slot.

In yet other embodiments of the present invention, a cam follower isprovided. In some of the embodiments including a cam follower, the camfollower can be of the roller type of cam follower. The roller typefollower typically includes a base member and a roller that is rotatablymounted relative to the base member. The roller is formed as a circularcylindrical shape having a longitudinal rotational axis defining thelength of the roller. The length of the roller can be greater than,equal to or less than the width of the cam surface of the movable cammember.

In those embodiments in which the length of the roller follower issmaller than or just equal to the width of the cam surface, theprovision of base circle arcuate sections is inadequate to carry theroller across the gap formed between the endwall of the slot and thecorresponding free edge of the movable cam member. Accordingly, in suchembodiments, additional structures are provided on the movable cammember and the hollow shaft. For example, a ramp tongue can define anexterior roller carrying surface. At least in the vicinity of the freeend of the ramp tongue, the exterior roller carrying surface desirablydefines the same radius of curvature as the radius of curvature of thebase circle band. The ramp tongue should be long enough n the directionof rotation of the hollow shaft so that the ramp tongue can extendbetween and across the maximum exposure of the adjacent slot when themovable cam member is oriented so as to produce this maximum exposure.The exterior roller carrying surface of each ramp tongue defines a widthmeasured in the direction of the longitudinal axis of the hollow shaft.This width is narrower than the width of the cam surface of the movablecam member and narrower than the length of the cylindrical surface ofeach roller follower. In order to accommodate the ramp tongue, whichextends from the end of either the leading ramp or the trailing ramp insome embodiments or from the front ear or back ear in other embodiments,a recess is defined through one end of the base circle band. In someembodiments, the recess is defined completely through the base circleband and the interior surface of the hollow shaft, much as the slot isformed. Alternatively, each recess can be provided with a bottom surfacethat is configured with a constant radius of curvature to form a sectionof a cylindrical surface, much as the cylindrical ear bearing surfaceswhich accommodate the ears of the associated movable cam memberembodiments. The provision of the bottom surface in the recess addsrigid support to the ramp tongue and permits the thickness of the ramptongue to be lessened while still being capable of bearing thecylindrical surface of the roller follower. Each recess communicateswith one of the ends of one of the grooves or one of the endwalls of theslot, depending upon the particular embodiment.

In still further embodiments, the ramp tongue can be one or moresaw-tooth shaped projections which meet with associated projectionsformed in the endwall of the slots. In such embodiments, the leading ortrailing ramp can define a biased free edge, as does the endwall of theslot.

In further accordance with the present invention, the actuating lobe ofthe movable cam member can define a cylindrical cavity in the noseportion where the nose ramp would be formed. A roller member with acylindrical surface then would be rotatably mounted in the cylindricalcavity so that the nose portion of the movable cam member would itselfbe formed as a rotatable roller. Accordingly, in such embodiments, thecam follower typically would be of the lever type or the tappet type.

In yet further accordance with the present invention, a second cammember could be mounted adjacent a movable cam member. The second cammember has a cam surface profile identical to that of the movable cammember and thus is essentially the twin of the movable cam member inthis respect. The second cam member is disposed beside the sidewall ofthe slot through which the movable cam member projects and is secured tothe hollow shaft so that the second cam member is not movable relativeto the hollow shaft. Moreover, both the movable cam member and the twinsecond cam member could be provided with rollers rotatably mounted attheir respective nose portions. This embodiment is particularly usefulwhen used in connection with a push rod engine in which the tappetsurface is part of a hydraulic valve lifter. In such embodiments, thetappet surface is formed with a circular cylindrical shaped surface. Thetappet also is keyed so that the central longitudinal axis of rotationof the circular cylindrical surface remains fixed in a transversedirection relative to the direction of rotational movement of the twincam members as the camshaft rotates. The keying of the tappet surfaceprevents it from rotating and getting out of alignment with the arcuatemovement of the twin cam members as the camshaft rotates. Thus, thetappet surface will engage each roller in a circular arc.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevated perspective view of components of a preferredembodiment of the present invention;

FIG. 2 is a partial cross-sectional view of components of an embodimentof the present invention as taken along the line of sight looking toward2--2 in FIG. 1;

FIG. is a partial cross-sectional view of the embodiment of FIG. 1 takenalong the line of sight looking toward 3--3 in FIG. 1;

FIG. 4 is a partial cross-sectional view of components of an embodimentof the present invention as taken along the line of sight looking toward4--4 in FIG. 1;

FIG. 5 is an elevated perspective view of components of anotherpreferred embodiment of the present invention;

FIG. 5a is yet another elevated perspective view of components ofanother preferred embodiment of the present invention;

FIG. 6 is an elevated perspective view in part and a cross-sectionalview in part of components of another alternative preferred embodimentof the present invention;

FIG. 7 is a partial cross-sectional view of components of still anotheralternative preferred embodiment of the present invention with somecomponents shown in phantom (dashed line);

FIG. 8 is an elevated perspective view of components of still anotherpreferred embodiment of the present invention;

FIG. 9 is an elevated perspective view of components which can be usedwith several of the preferred embodiments of the present invention;

FIG. 10 is an elevated perspective view of alternative components whichcan be used with several further preferred embodiments of the presentinvention;

FIG. 11 is yet another elevated perspective view of components ofanother preferred embodiment of the present invention;

FIG. 12 illustrates a partial schematic view of an internal combustionengine embodiment according to the present invention; and

FIG. 13 illustrates an expanded detail schematic view of a portion ofthe embodiment shown in FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In some preferred embodiments of the present invention, a single movablecam lobe member is provided for actuating a roller cam follower. In someof these roller follower embodiments of the present invention, thelength of the roller follower engaging the single cam lobe is longerthan the width of the cam lobe. In other of these roller followerembodiments of the present invention, the length of the roller followeris less than or equal to the width of the single cam lobe. In yet otherpreferred embodiments of the present invention, the nose of a single camlobe member is provided with a roller to actuate a lever cam follower ora tappet cam follower. In still further preferred embodiments of thepresent invention, both noses of a split cam lobe are provided with aroller to actuate a lever cam follower or a tappet cam follower. In yetfurther preferred embodiments, the cam follower forms part of ahydraulic lifter.

Reference now will be made in detail to the present preferredembodiments of the present invention, several examples of which areillustrated in the accompanying drawings. Each example is provided byway of explanation of the invention, not limitation of the invention. Infact, it will be apparent to those skilled in the art that variousmodifications and variations can be made in the present inventionwithout departing from the scope or spirit of the invention. Forinstance, features illustrated or described as part of one embodiment,can be used on another embodiment to yield a still further embodiment.Thus, it is intended that the present invention cover the modificationsand variations of this invention provided they come within the scope ofthe appended claims and their equivalents.

Examples of components of preferred embodiments of the present inventionare indicated generally by the designating numeral 20 in FIGS. 1, 2, 5,5a, 7, 12 and 13. In accordance with some embodiments of the actuatingapparatus of the present invention, a cam follower can be provided. Thecam follower defines a surface which engages the actuating surface of acam member (described in detail hereafter). For some embodiments of thepresent invention, the cam follower preferably is a roller typefollower. However, in instances in which use of a roller type followeris impractical, a lever type follower or a tappet follower can be used.A lever type follower defines a cam engaging surface that pivots aboutan axis. A tappet type follower defines a cam engaging surface thatmoves longitudinally n a path toward and away from the actuating surfaceof the cam member. One or the other type of follower s usually desired,depending on the particular application. As embodied herein and shown inFIGS. 1 (in phantom), 2, 7 (in phantom) and 13 for example, a camfollower is generally designated by the designating numeral 86.

The roller type follower typically includes a base member and a rollerthat is rotatably mounted relative to the base member. As embodied andshown in FIGS. 1 and 2 for example, cam follower 86 is of the rollertype and includes a base member 88 and a roller 90. Roller 90 isrotatably mounted via an axle 92 in the opening of a fork formed byopposed depending members 94 extending from base member 88. Roller 90defines an elongated cylindrical surface 96 and is rotatable about acentral longitudinal axis that is disposed coincident with axle 92. Basemember 88, roller 90, axle 92, and cam surface 54 preferably are formedof a rigid material such as steel or other strong metal used forfabricating roller followers and cams for automotive applications.

As shown in FIG. 1 for example, the length of roller cylindrical surface96 as measured in the direction of axle 92 can be longer than the widthof the cam surface 54 of the movable cam member 42 (describedhereafter). In such embodiments, roller cylindrical surface 96 extendsbeyond the opposite edges 60 of the cam surface 54 when the rollercylindrical surface 96 engages the cam surface 54. In an alternativeembodiment such as shown n FIG. 5 for example, the length of rollercylindrical surface 96 can be less than the width of the surface 54 ofthe movable cam member 42. In a yet further embodiment of the presentinvention such as shown in FIG. 5a for example, the length of rollercylindrical surface 96 can be equal to the width of the surface 54 ofthe movable cam member 42.

In further accordance with the present invention, an elongated hollowshaft is provided. The hollow shaft defines a longitudinal axis, anexterior surface, an interior surface, and a slot defined through theinterior and exterior surfaces. The hollow shaft can be formed in any ofthe conventional methods for making camshafts. For example, castingmethods can be used to form the hollow shaft with slots. Alternatively,the shaft can be machined, and features such as the slot can be formedby electrodischarge machining of the slot. As embodied herein and shownin FIGS. 9 and 10 for example, an elongated hollow shaft 22 is providedwith a generally cylindrically shaped wall. The generally cylindricalwall of hollow shaft 22 has an exterior surface 26 and an interiorsurface 28. As shown in FIGS. 9 and 10 for example, interior surface 28of hollow shaft 22 runs the entire length of hollow shaft 22, andportions of interior surface 28 define circular cylindrically shapedbearing surfaces 29 that can be used to rotatably support a solid shaft(described hereafter) as well as other members. As shown in FIGS. 9 and10 for example, hollow shaft 22 defines a longitudinal axis indicated bythe designating numeral 24. Longitudinal axis 24 is a central axis ofrotation of hollow shaft 22.

As shown for example in FIGS. 9 and 10, a slot is indicated generally bythe designating numeral 30 and is defined through exterior surface 26and interior surface 28. In other words, slot 30 is cut completelythrough the cylindrical wall of hollow shaft 22. Slot 30 is defined atleast in part by a pair of opposed sidewalls 32 (FIGS. 3, 5, 6, 9 and 10for example) and a pair of opposed endwalls 34 (FIGS. 1, 2, 5, 6, 7, 9and 10 for example) disposed between sidewalls 32. (When FIG. 1 is usedto illustrate the FIG. 2 configuration of the movable cam member and thehollow shaft, then the designating letter A indicates a slot endwall34.) Each slot sidewall 32 extends in a direction transverse tolongitudinal axis 24. The sidewalls may be continuous (FIGS. 1, 3, and 9for example). The endwalls may be continuous (FIGS. 1 and 8 for example)or discontinuous (FIGS. 5, 9 and 10 for example). A separate slot 30will be defined in the hollow shaft for each movable cam member(described hereafter) that is desired. Thus, a single hollow shaft 22might be provided with one or more slots 30 arranged along the length ofthe hollow shaft.

In further accordance with the present invention, the exterior surfaceof the hollow shaft defines a base circle band, which is a portion ofthe exterior surface of the hollow shaft that extends in acircumferential direction between the endwalls of each slot that isdefined through the hollow shaft. Preferably, the base circle bandextends in the longitudinal direction of the hollow shaft, beyond theportion of the hollow shaft bounded between the sidewalls of the slot.Thus, the width of the base circle band (as measured in the direction ofthe longitudinal axis of the hollow shaft) is wider than the width ofthe slot (as measured between the sidewalls of the slot). The portion ofthe exterior surface of the hollow shaft defined by the base circle bandhas a constant radius of curvature and is intended to carry the camfollower when the follower is not riding on the cam surface of themovable cam (described hereafter). As shown in FIGS. 1, 2, 3, 4, 5, 5a,6, 7, 8, 9, 10 and 11, exterior surface 26 of hollow shaft 22 defines abase circle band 36, which extends between endwalls 34 of slot 30. Basecircle band 36 defines a portion of exterior surface 26 having aconstant radius of curvature extending between the respective endwallsof slot 30. Base circle band 36 is the portion of the exterior surfaceof hollow shaft 22 that carries a cam follower such as a roller followerwhen the follower is not riding on the cam surface 54 of the cam lobemember 42 (described hereafter).

In further accordance with some embodiments of the present invention,the hollow shaft further defines base circle arcuate sections thatprovide upper cam receiving surfaces. The base circle arcuate sectionsare disposed so as to carry the peripheral edges of a cam follower suchas a roller follower. The base circle arcuate sections are disposedbeside the sidewalls and near the vicinity of the endwalls of the slotthrough which the movable cam member (described hereafter) extends. Thebase circle arcuate sections carry the roller follower over the gap thatcan be produced between the endwall of the slot and the free edge of themovable cam member that meets the endwall of the slot. At least in thevicinity where the base circle arcuate sections extend to one of theendwalls of the slot, each upper cam receiving surface defines the sameradius of curvature as the base circle band. The provision of the basecircle arcuate sections is primarily intended for those embodiments ofthe invention in which the longitudinal length of the roller followerexceeds the width of the cam surface. In such embodiments, the ends ofthe follower extend beyond the opposite edges of the cam surface.

As embodied herein and shown in FIGS. 1 and 2 for example, a pair ofbase circle arcuate sections 38, 40 are provided on the exterior surfaceof hollow shaft 22 in the vicinity of one of endwalls 34 of slot 30where sidewalls 32 of slot 30 meet this endwall 34 of slot 30. Each basecircle arcuate section 38, 40 defines an upper cam receiving surface 39,41, respectively, having the same radius of curvature as base circleband 36. Preferably, as shown in FIG. 1 for example, each upper camreceiving surface 39, 41 extends continuously from one of the peripheraledges of base circle band 36. A similar pair of base circle arcuatesections is provided in the vicinity of the opposite endwall of slot 30,but these base circle arcuate sections are not completely visible in theview shown in the FIGS. 1 and 2. Thus, in the embodiment shown partiallyin FIG. 1 for example, four base circle arcuate sections are provided.

The base circle arcuate section aspect of the present invention perhapss more clearly illustrated in FIG. 9 in which four base circle arcuatesections 38, 40, 238, 240, are provided with respective upper camreceiving surfaces 39, 41, 239, 241. In the embodiment shown in FIG. 9for example, the two base circle arcuate sections 40, 240 disposed toone side of slot 30 are integral with each other, and the other two basecircle arcuate sections 38, 238 disposed to the other side of slot 30are integral with each other. Moreover, as is partially shown in FIGS. 1and 9 for example, the two base circle arcuate sections disposed to oneside of slot 30 are integral with the periphery of the base circle bandand together extend around the full 360° of hollow shaft 22 and form abase circle ring with a continuous upper cam receiving surface thatcarries roller 90 of roller follower 86. Each upper cam receivingsurface 39, 41, 239, 241 has a radius of curvature equal to the radiusof curvature of base circle band 36 and preferably is integral with basecircle band 36, as shown in FIGS. 1 and 9 for example. Each base circlearcuate section has a minimum length that is long enough to extend thefull arcuate distance that slot 30 is exposed when the movable cammember 42 (described hereafter) projecting through slot 30 is orientedto expose the maximum gap between the slot endwall 34 and the surface ofthe movable cam member that abuts with the slot endwall.

In yet further accordance with the present invention, the hollow shaftis provided with a channel defined in the interior cylindrical bearingsurface. The channel has channel sidewalls and a channel bearingsurface. The channel bearing surface is disposed generally opposite tothe slot defined through the hollow shaft. The channel bearing surfaceis configured to rotatably support the movable cam member inside thehollow shaft. The channel sidewalls are generally disposed transverselyto the longitudinal axis of the hollow shaft. As embodied herein andshown in FIGS. 3, 9 and 10 for example, the channel s defined by achannel bearing surface 46 and channel sidewalls 48. The channel has nochannel endwalls disposed between channel sidewalls 48. Thus, thechannel extends to the endwalls of the slot on the interior cylindricalbearing surface. The provision of the channel is accommodated by theprovision of base circle band 36 and provides an additional thickness ofmaterial at the location of the hollow shaft where the movable cammember is to be supported by the interior surface of the hollow shaft.As noted above, the base circle band extends in the longitudinaldirection of the hollow shaft, beyond the portion of the hollow shaftthat is intersected by the sidewalls of the channel.

In addition, all internal corners (where three surfaces meet at anangle) and joints (where two surfaces meet at an angle) are filleted toavoid the stress concentrations associated with sharp corners andjoints. As shown in FIG. 3 for example, a surface of constant radius,rather than a sharp, right angled joint, is formed where channelsidewalls 48 meet the periphery of channel bearing surface 46.Importantly, the elimination of sharp, right angle joints helps toreduce structural stresses in hollow shaft 22 where the movable cammember 42 is to be supported.

In further accordance with the present invention, a movable cam memberis provided. The movable cam member defines an actuating lobe and aseating member. The actuating lobe and the seating member preferably areintegrally connected to each other and typically will be manufactured asa unitary component of the present invention. For example, powdermetallurgical casting techniques can be used to manufacture a movablecam member. As embodied herein and shown in FIGS. 1, 2, 3, 4, 5, 5a, 6,7, 8, and 11 for example, a movable cam member 42 can be disposed so asto project through the slot of the hollow shaft. As shown for example inFIGS. 2, 3, 4, 6, and 7, movable cam member 42 defines a seating member56 having an outer cylindrical shaft bearing surface 58, which isconfigured to rotatably engage channel bearing surface 46 of theinterior surface of hollow shaft 22.

As embodied herein and shown in FIGS. 2, 3, 4, 6, 8 and 11 for example,movable cam member 42 further defines an actuating member (or lobe) 52,which defines a cam surface 54. Cam surface 54 is configured to projectthrough slot 30 of hollow shaft 22 when outer cylindrical shaft bearingsurface 58 is disposed to rotatably engage channel bearing surface 46,which is defined in the interior surface of hollow shaft 22. As shown inFIG. 3 for example, the width of cam surface 54 of movable cam member 42is bounded by opposed edges 60.

As shown for example in FIGS. 1, 2, 5, 5a, and 7, cam surface 54 is aportion of movable cam member 42 that contacts and carries the camfollower (shown in phantom n FIGS. 1, 5, 5a, and 7). As shown in FIGS. 2and 4 for example, cam surface 54 is configured to engage the camfollower and defines a profile which includes a nose ramp 62, a leadingramp 64, and a trailing ramp 66. Typically, the profile of the camsurface in the vicinity of the leading ramp and the vicinity of thetrailing ramp has a greater radius of curvature than the radius ofcurvature of the base circle band. Relative to leading ramp 64 andtrailing ramp 66, nose ramp 62 is that portion of cam surface 54 that isdisposed the greatest distance away from outer shaft bearing surface 58of seating member 56 of movable cam member 42. In other words, the noseramp is disposed farther from the exterior surface 26 of hollow shaft 22when outer cylindrical shaft bearing surface 58 of movable cam member 42is disposed to rotatably engage channel bearing surface 46 of hollowshaft 22. Nose ramp 62 is similarly disposed the greatest distance awayfrom longitudinal axis 24 than is either the leading ramp 64 or thetrailing ramp 66. Leading ramp 64 forms the portion of cam surface 54that the cam follower engages before the cam follower engages nose ramp62 as the hollow shaft rotates around its longitudinal axis 24.Similarly, trailing ramp 66 forms that portion of cam surface 54 thatthe cam follower engages after riding over nose ramp 62 during therevolution of hollow shaft 22.

In further accordance with the present invention, an elongated innershaft is provided. As embodied herein and shown in FIG. 3 for example,an elongated inner shaft 68 defines an axis of rotation 70 along itslength. As shown in FIGS. 1, 2, 5, 5a, 6, and 7 for example, elongatedinner shaft 68 preferably s a solid shaft, but can be hollow so long asthe hollow form maintains the structural integrity required foroperating in the intended environment of the inner shaft.

In yet further accordance with the present invention, means are providedfor nonrotatably connecting the inner shaft and the movable cam memberfor simultaneous rotational movement. In one embodiment of the means fornonrotatably connecting the inner shaft and the movable cam member forsimultaneous rotational movement, two mating sets of radially extendingspline members are provided. One set of spline members is provided onthe outer surface of the inner shaft, and a second set of spline membersis provided on the internal circumference of an opening formedtransversely through the movable cam member. The two sets of splinemembers are configured to interlock with one another to prevent relativerotation between the inner shaft and the movable cam member.

As embodied herein and shown in FIGS. 2 and 3 for example, the means fornonrotatably connecting the inner shaft and the movable cam member forsimultaneous rotational movement can include a plurality of radiallyextending spline members 72 defined on the outer surface of inner shaft68. As embodied herein and shown in FIG. 4 for example, a plurality ofradially extending spline members 74 defines a generally centralizedopening 76 through movable cam member 42. Each spline member 74 extendsin a direction parallel to the direction in which the width of camsurface 54 is measured between edges 60 (FIG. 3 for example). Theconfiguration of the outer surface of inner shaft 68 formed by splinemembers 72 matches and mates with the configuration of movable cammember opening 76 formed by spline members 74. The radially extendingspline members 74 defining opening 76 transversely through the movablecam member 42 are configured to interlock with the radially extendingspline members 72 defined on the outer surface of the inner shaft 68.Accordingly, inner shaft 68 can be nonrotatably keyed through opening 76of movable cam member 42 as shown in FIGS. 1-3 for example.

An example of an alternative preferred embodiment for the means fornonrotatably connecting the inner shaft and the movable cam member forsimultaneous rotational movement is a non-circular cross-section innershaft and a bushing defining a mating non-circular opening. One suchembodiment having a hexagonal symmetry for the non-circular matingsurfaces is shown for example in FIGS. 3, 4 and 5 of each of U.S. Pat.No. 4,770,060 to Elrod et al. U.S. Pat. No. 4,771,742 to Nelson et al,and U.S. Pat. No. 4,917,058 to Nelson et al, which U.S. Patents againare hereby incorporated herein by reference.

In another alterative embodiment of the means for nonrotatablyconnecting the inner shaft and the movable cam member for simultaneousrotational movement, a shrink-fitting technique can be used. In suchshrink-fitted embodiment, inner shaft 68 can be cylindrical with acircular cross-section, and central opening 76 can be formed with acircular cross-section having a diameter slightly less than the diameterof the cylindrical inner shaft 68. During assembly, inner shaft 68 wouldbe cooled to a temperature sufficient to reduce its diameter, andmovable cam member 42 would be heated to a temperature sufficient toincrease the diameter of its opening 76. The increased diameter ofmovable cam member opening 76 accomplished by heating, and the decreaseddiameter of inner shaft 68 accomplished by cooling, would be sufficientto enable opening 76 of the heated movable cam member 42 to slip overthe diameter of inner shaft 68. Upon bringing both inner shaft 68 andcam lobe member 42 to room temperature, the opening of movable cammember 42 would be shrink-fitted and thus nonrotatably secured to theouter surface of inner shaft 68.

In a yet further example of another alternative embodiment for the meansfor nonrotatably connecting the inner shaft and the movable cam member,as shown for example in FIG. 7, a raised key member extends from movablecam member opening 76 in a direction opposite to nose ramp 62 and towardthe center of opening 76, while a key recess such as shown at 79 in FIG.7 is defined in the outer surface of inner shaft 68 wherever a movablecam member is to be located circumferentially relative to the outersurface of inner shaft 68. Accordingly, in this latter preferredembodiment, each key recess 79 could extend substantially the fulllength of inner shaft 68 in order to permit inner shaft 68 to passthrough central opening 76 of each movable cam member 42 during assemblyof the apparatus 20. Thus, if for example four movable cam members areto be mounted at four different circumferential locations, then four keyrecesses could be formed as continuous grooves in the outer surface ofinner shaft 68 at different circumferential locations about the outersurface of inner shaft 68.

One advantage of the FIG. 7 and shrink-fitted embodiments over theembodiments shown in FIGS. 2 and 4 for example is the greater radialthickness of material that exists between the movable cam member opening76 and outer cylindrical shaft bearing surface 58 that is afforded bythe shrink-fit embodiment and the embodiment shown in FIG. 7 versusthose embodiments shown in FIGS. 2 and 4 for example. This greaterthickness of material forming seating member 56 is likely to be strongerand better able to bear the stresses on the movable cam member duringoperation of the apparatus 20.

In some alternative embodiments of the present invention, the movablecam member can define a front stop surface and a back stop surface. Asembodied herein and shown in FIGS. 2, 6 and 7 for example, movable cammember 42 defines a front stop surface 78 which extends from and formsan edge 80 with the end of leading ramp 64. Edge 80 is the free edge ofleading ramp 64 that is disposed opposite from nose ramp 62. Front stopsurface 78 is configured and disposed to conform to one of endwalls 34of slot 30. As embodied herein and shown in FIGS. 2 and 7 for example,movable cam member 42 defines a back stop surface 82 which extends fromand forms an edge 84 with the end of trailing ramp 66. Edge 84 is thefree edge of trailing ramp 66 that is disposed opposite from nose ramp62. Back stop surface 82 is likewise configured and disposed to conformto the other of endwalls 34 of slot 30.

FIGS. 2 and 4 illustrate alternative embodiments of movable cam member42 and hollow shaft 22. The embodiment shown in FIG. 2 already has beendescribed above. Turning now to the two embodiments shown in FIGS. 4 and10 for example, the exterior surface of hollow shaft 22 defines a pairof grooves. One end of each groove is connected to one of the twoopposite ends of slot 30, while the other end of each of the grooves isformed by a groove endwall 98. When FIG. 1 is used to illustrate theFIG. 4 configuration of the movable cam member and the hollow shaft,then the designating letter A indicates a groove endwall 98. Each groovehas a bottom surface that defines an exterior cylindrical ear bearingsurface 100. The exterior cylindrical ear bearing surface 100 is formedas a section of a cylindrical surface. As shown in FIGS. 4 and 10 forexample, one of the exterior cylindrical ear bearing surfaces 100 beginsat one end of the slot 30, and the other exterior cylindrical earbearing surface ends at the opposite end of the slot formed through thewall of the hollow shaft. Similarly, the other end of each exteriorcylindrical ear bearing surface begins at one of the groove endwalls 98.

In further accordance with some embodiments of the present invention,the movable cam member can include ear members which extend from theleading ramp and the trailing ramp. These ear members extend the profileof the cam surface without requiring a larger slot and the weakening ofthe hollow shaft that would accompany a larger slot. The exteriorsurface of the ear members can provide a transition from the curvaturewhich defines the cam surface to the curvature which defines the basecircle band. As embodied herein and shown in FIGS. 4 and 6 for example,movable cam member 42 further defines a front ear 102. Front ear 102defines an exterior surface that extends from the end of leading ramp 64disposed opposite from nose ramp 62. The exterior surface of front ear102 is designated 104. At least the portion of exterior surface 104 offront ear 102 in the vicinity of the free end of the front ear in theFIG. 4 embodiment, is defined by the same radius of curvature thatdefines base circle band 36 of hollow shaft 22. Front ear 102 furtherdefines an inner cylindrical ear bearing surface 106, which is disposedopposite front ear exterior surface 104. Inner cylindrical ear bearingsurface 106 defines the same constant radius of curvature that definesexterior cylindrical ear bearing surface 100 of the grooves in hollowshaft 22. Moreover, inner cylindrical ear bearing surface 106 of frontear 102 and outer cylindrical shaft bearing surface 58 further definethe boundary of a front ear cavity 108. Thus as shown for example inFIG. 4, exterior cylindrical ear bearing surface 100 of hollow shaft 22and interior surface 28 of hollow shaft 22 define opposite surfaces of aportion of hollow shaft 22 that can slide into and out of front earcavity 108 as movable cam member 42 rotates its outer cylindrical shaftbearing surface 58 relative to channel bearing surface 46 of theinterior surface of hollow shaft 22.

In the embodiments including ears on the movable cam member andproviding ear cavities therein for the reception of a portion of thehollow shaft defined by exterior cylindrical ear bearing surface 100 andinterior surface 28 such as shown in FIG. 4 for example, the strength ofthe hollow shaft in the vicinity of slot 30 can be increased by virtueof the added portion of the hollow shaft that is receivable in the earcavities.

In addition, and as shown in FIG. 4 for example, movable cam member 42further defines a back ear 110. Back ear 110 defines an exterior surfacethat extends from the end of trailing ramp 66 disposed opposite fromnose ramp 62. The exterior surface of back ear 102 is designated 112. Atleast the portion of exterior surface 112 of back ear 110 in thevicinity of the free end of the back ear, is defined by the same radiusof curvature that defines base circle band 36 of hollow shaft 22. Backear 110 further defines an inner cylindrical ear bearing surface 106,which is disposed opposite back ear exterior surface 112. Innercylindrical ear bearing surface 106 defines the same constant radius ofcurvature that defines exterior cylindrical ear bearing surface 100 ofthe grooves in hollow shaft 22. Moreover, inner cylindrical ear bearingsurface 106 of back ear 110 and outer cylindrical shaft bearing surface58 of movable cam member 42 further define the boundary of a back earcavity 114. Thus, exterior cylindrical ear bearing surface 100 of hollowshaft 22 and interior surface 28 of hollow shaft 22 define oppositesurfaces of a portion of hollow shaft 22 that can slide into and out ofback ear cavity 114 as movable cam member 42 rotates its outercylindrical shaft bearing surface 58 relative to channel bearing surface46 of the interior surface of hollow shaft 22.

In those preferred embodiments of the present invention in which thelength of the roller follower is smaller than or just equal to the widthof the cam surface, the provision of base circle arcuate sections isinadequate to carry the roller across the gap formed between the endwallof the slot and the corresponding free edge of the movable cam member.Accordingly, in such embodiments, additional structures provide anuninterrupted transition of the roller from the trailing or leading rampto the base circle band of the exterior surface of the hollow shaft.Examples of these additional structural provisions are shown in theembodiments illustrated in FIGS. 5, 5a, 6, 9, 10 and 11.

Thus, in two further alternative embodiments shown in FIGS. 5 and 6 forexample, each of the leading ramp and trailing ramp of movable cammember 42 can further define a ramp tongue 120. Each ramp tongue 120defines an exterior roller carrying surface 122. At least the portion inthe vicinity of the free end of each exterior roller carrying surface122 of each ramp tongue 120, defines the same radius of curvature as theradius of curvature of base circle band 36 of hollow shaft 22.

Importantly, each ramp tongue 120 must be long enough in the directionof rotation of hollow shaft 22 so that the ramp tongue can extend beyondand across the maximum exposure of the adjacent slot (in embodimentslike those of FIGS. 5, 6 and 10) defined in the hollow shaft when themovable cam member is displaced so as to produce such maximum exposure.This maximum exposure position is shown in each of FIGS. 5 and 6 forexample. Such maximum exposure occurs when the outer cylindrical shaftbearing surface .58 of the movable cam member 42 is disposed to engagechannel bearing surface 46 of the hollow shaft while the movable cammember is disposed the maximum amount in a direction rotating away fromthe adjacent slot endwall 34 of the hollow shaft. Moreover, the exteriorroller carrying surface 122 of each ramp tongue 120 defines a widthmeasured in the direction of longitudinal axis 24 of hollow shaft 22.This width of each exterior roller carrying surface 122 is narrower thanthe width of cam surface 54 of movable cam member 42 and narrower thanthe length of cylindrical surface 96 of roller 90.

Furthermore, in accordance with some embodiments of the presentinvention, the exterior surface of the hollow shaft further defines apair of recesses. Each recess is defined through one end of the basecircle band. In some embodiments, each recess is defined completelythrough both the base circle band and the interior surface of hollowshaft, in much the same way that the slot is cut completely through thecylindrical wall of the hollow shaft. In other embodiments, the recessis provided with a bottom surface which desirably is configured with aconstant radius of curvature to form a section of a cylindrical surface.In yet other embodiments, each recess is provided with a partial bottomsurface and is partially cut completely through the cylindrical wall ofthe hollow shaft. The provision of either the complete or partial bottomsurface adds rigid support to the ramp tongue, and thus allows thethickness of the ramp tongue to be less than it otherwise would need tobe.

As embodied herein and shown for example in FIGS. 5, 6, 9, and 10, theexterior surface of hollow shaft 22 further defines a pair of recesses.Each recess is defined through one end of base circle band 36 and isindicated generally in FIGS. 5, 6, 9 and 10 by the designating numeral118. As shown in FIG. 5 for example, recess 118 is defined completelythrough base circle band 36 and the interior surface of hollow shaft 22,much as slot 30 is formed. Alternatively, as shown in FIG. 6 forexample, recess 118 is provided with a bottom surface 121, which definesan exterior cylindrical tongue bearing surface. Preferably, eachexterior cylindrical tongue bearing surface is configured with aconstant radius of curvature to form a section of a cylindrical surface.In such embodiments, each of the ramp tongues defines an innercylindrical tongue bearing surface having the same radius of curvaturethat defines the exterior cylindrical tongue bearing surface.

Furthermore, as shown in the embodiment illustrated in FIG. 10 forexample, recess 118 is provided with a partial bottom surface 121. Theprovision of bottom surface 121 provides additional rigid support toramp tongue 120, and thus the thickness of ramp tongue 120 is less inthe FIG. 6 embodiment than it is in the FIG. 5 embodiment for example.In addition, in the embodiments shown in FIGS. 5 and 9 for example, eachrecess 118 communicates with the slot and interrupts one of the slotendwalls 34. Similarly, in the embodiment shown in FIG. 10 for example,each recess 118 can communicate with one of the ends of one of thegrooves that is disposed opposite the endwalls of slot 30. It isdesirable if each recess is centrally and symmetrically disposedrelative to the width of the adjacent slot (as shown in FIG. 5 forexample) or adjacent groove (as shown in FIG. 10 for example) and isconfigured to receive one of ramp tongues 120.

Though not shown in the Figs., the configuration of the ramp tongue thatwould be used in conjunction with the hollow shaft shown in FIG. 10would be a combination of the configuration shown for the ramp tongue inFIG. 5 and that shown for the ramp tongue in FIG. 6. The free end of theramp tongue would be configured like the ramp tongue shown in FIG. 6.The ramp tongue's intermediate portion, which is the portion that joinedwith the ear portion of the movable cam on the side and with the leadingor trailing ramp portion of the movable cam on the end, would beconfigured as shown in FIG. 5. Thus, the intermediate portion of theramp tongue would be thicker than the free end of the ramp tongue.

In some embodiments (FIGS. 1 and 2 for example), the free edge of theleading or trailing ramp of the movable cam member can be moved to aposition where it abuts against and mates with the nearby endwall 34 ofthe slot 30. In other embodiments (FIGS. 1, 4 and 10 for example), thefree edge of the front or back ear of the movable cam member can bemoved to a position where it abuts against and mates with the nearbyendwall 98 of the groove. In yet other embodiments (FIGS. 5 and 6 forexample), when the free edge of front stop surface 78 (or back stopsurface 82, which is not shown in FIGS. 5 and 6) of the leading ortrailing ramp of the movable cam member moves to a position where itabuts against and mates with the nearby endwall 34 of the slot, the freeedge of the ramp tongue 120 of the movable cam member 42 moves to aposition where it abuts against and mates with the nearby endwall 119 ofthe recess 118. In still further embodiments (FIG. 10 for example), whenthe free edge of the front or back ear of the movable cam member movesto a position where it abuts against and mates with the nearby endwall98 of the groove, the free edge of the ramp tongue of the movable cammember moves to a position where it abuts against and mates with thenearby endwall 119 of the recess.

In two further alternative embodiments shown in FIGS. 5a and 11 forexample, each leading or trailing ramp 124 defines a free edge 126 whichextends at a bias relative to the direction of movement of movable cammember 42 within slot 30. In addition, each endwall of the slot 30 isdefined by a biased edge 128 configured to abut uninterruptedly againstfree edge 126 of one of leading or trailing ramps 124 when the movablecam member is disposed the maximum amount in a direction rotating towardthe adjacent endwall of the slot formed in hollow shaft 22. Furthermore,the biasing of free edge 126 and biased edge 128 are configured so thatwhen one of the leading or trailing ramps is disposed so that its freeedge 126 abuts against the adjacent biased edge 128 of the endwall ofthe slot, there is sufficient coverage of the gap produced on theopposite trailing or leading ramp so that sufficient support exists tocarry the roller and prevent the roller from falling into any gap formedbetween the free edge 126 and corresponding adjacent biased edge 128 ofthe respective trailing or leading ramp. Moreover, the pattern shown inFIG. 11 can be duplicated a number of times instead of just the singleinstance of the pattern used in the embodiment illustrated in FIG. 11.Accordingly, a saw tooth type configuration is contemplated wherein anumber of repetitions of the pattern shown in FIG. 11 are provided forbiased edge 128 and free edge 126.

In further accordance with some embodiments of the present invention,the actuating lobe of the movable cam member defines a cylindricalcavity in the free end thereof. A roller member with a circularcylindrical surface is rotatably mounted in the cylindrical cavity. Asembodied herein and shown in FIG. 7 for example, the outline of acylindrical cavity is designated in phantom (dashed line) by the numeral130. A roller 132 has a cylindrical exterior surface 134 and isrotatably mounted, as by a journal 136 extending in the longitudinaldirection of cylindrical cavity 130 and cylindrical roller 132. A camfollower of the lever type is indicated generally by the numeral 86 andincludes a rocker arm shown in phantom (dashed line) and indicated bythe numeral 138. (Alternatively, a tappet type follower such as shown inFIG. 13 also can be used). Rocker arm 138 is rotatably mounted about apivot 140. As movable cam member 42 and hollow shaft 22 rotate togetherin the clockwise direction of arrow 142, the outline of actuating lobe52 takes up the successive positions indicated in dashed line by thedesignating numeral 144 and then 146. Roller surface 134 engages thesmoothly curving actuating surface 148 of rocker arm 138 as actuatinglobe 52 of movable cam member 42 rotates in the direction of arrow 142.

In still further embodiments of the present invention, a second cammember is mounted adjacent a movable cam member. The second cam memberdesirably is fixed to the exterior surface of the hollow shaft at aposition adjacent one of the sidewalls of a slot. The movable cam memberis constructed and operates as described above and in Nelson et al U.S.Pat. No. 4,917,058, Nelson et al U.S. Pat. No. 4,771,742, and Elrod etal U.S. Pat. No. 4,770,060, hereby incorporated herein by reference.Typically, the second cam member is not movable relative to the hollowshaft, but may in some embodiments be movable out of phase relative tothe crankshaft (designated by the numeral 186 in FIG. 13) such as isexplained in the Patents to Nelson et al and Elrod et al alreadyincorporated herein by reference. The second cam member can beconsidered a twin of the movable cam member insofar as the second cammember defines the indentical cam surface profile as the movable cammember. In other words, the radii of curvature of the leading ramps ofthe twin cam members are the same, as are the radii of curvature of thetrailing ramps and the radii of curvature of the nose portions of therespective movable cam member and its twin second cam member. Moreover,the base circle band defines the same radius of curvature for both ofthe twin cam members. Furthermore, in some embodiments, the nose portionof the cam surface of the second cam member can be formed by the outersurface of a second circular cylindrical roller member. Moreover, boththe movable cam member and the second cam member can be provided withrollers rotatably mounted at their respective nose portions.

As embodied herein and shown in FIG. 8 for example, a movable cam member42 is configured in the same fashion as previously described withreference to FIG. 7 and is similarly numbered with reference characters.Mounted adjacent movable cam member 42 is a second cam member 150.Second cam member 150 is identically configured as to its profile in allrespects as movable cam member 42. Thus, second cam member 150 has aroller surface 152 of a cylindrical roller 154 mounted rotatably on ajournal 156. While a lever type follower is not shown in FIG. 8 in orderto permit easier viewing of other aspects of this embodiment, a levertype cam follower (similar to that shown in FIG. 7 for example) could beemployed.

In the embodiments having rotatable rollers in the nose portion of asingle movable cam member or a twin pair of cam members, each movablecam member, either alone or together with a twin second cam member asthe case may be, is disposed to actuate a single cam follower. In otherwords, in some embodiments, such as an engine employing push rods, asingle follower is provided to engage the rollers of the nose portionsof both cam surfaces of the twin cam members. Each such follower can beformed as the tappet surface of a hydraulic valve lifter. This tappetsurface desirably defines a circular cylindrically shaped surface forengaging the cam surfaces of the movable cam member and its twin secondcam member. As noted above, in some embodiments the hydraulic valvelifter forms part of a push rod engine. As embodied herein and shown inFIG. 12 for example, a portion of a push rod engine is schematicallyrepresented and generally indicated by the designating numeral 174. Asshown in FIG. 12 for example, a socket 158 of a hydraulic valve lifter,which is generally designated 160, is shown schematically. A push rod168 mechanically connects the valve lifter 160 and a rocker arm 138,which in turn acts against one end of a valve stem 169 which passesthrough a cylinder head 172. A valve head 170 is formed on the oppositeend of valve stem 169. A cylinder wall 178 defines a cylinder chamber180 in which a piston 182 is connected via a connecting rod 184 to acrankshaft 186, which also drives the camshaft actuating member 20 via atiming belt, which is not shown in FIG. 12 but is conventional in theart. A spark plug 188 ignites the fuel-air mixture entering thecombustion chamber 190 of cylinder 178. A manifold 192 communicates withcombustion chamber 190 via valve opening 194 and may be either aninduction manifold or an exhaust manifold depending upon whether valveopening 194 is an intake valve opening or an exhaust valve opening, asknown in the art. As embodied herein and shown in FIG. 13 for example,the free end of a valve lifter piston 166 forms a tappet having acircular cylindrically curved tappet surface 196, which engages thecylindrical surface 134, 152 of the cylindrical rollers 132, 154 mountedin the nose portions of second cam member 150 and movable cam member 42.

In further accordance with the present invention, means are provided forholding the tappet surface shared by the twin cam members at a fixedorientation relative to the path of rotation of the twin cam members. Asembodied herein and shown for example in FIG. 13, the means for holdingthe tappet surface at a fixed orientation relative to the path ofrotation of the movable cam member and the second cam member includes akey member 162 and a groove 164 for slidably receiving the key member.Groove 164 is configured to restrict movement of key member 162 to onepredetermined path, wherein only one of the key member and the groove isconnected to the tappet. In the embodiment shown in FIG. 13 for example,groove 164 is connected to the tappet by being defined in piston 166.Desirably, the one predetermined path of movement of the key memberdefines a straight line. The restriction of key 162 to move only withingroove 164 prevents the piston 166 of the lifter 160 from rotatingrelative to its socket 158. In this way, the central longitudinal axisof rotation of the cylindrical surface remains fixed in a transversedirection relative to the direction of rotational movement of the cammembers as the camshaft rotates. In other words, the centrallongitudinal axis of curvature of the tappet surface is maintainedcoincident with the central longitudinal axis of rotation of each of thecam members. Since the tappet surface cannot rotate, it engages eachroller in a fashion similar to the way roller surface 134 engagessmoothly curving rocker arm actuating surface 148 as shown in the viewof FIG. 7 for example.

In embodiments such as shown in FIGS. 1, 2, 3, 4 and 9, the base circlearcuate sections such as base circle arcuate sections 38, 40, 238, 240are provided with upper cam receiving surfaces 39, 41, 239, 241,respectively, on which the peripheral edges of cylindrical rollers 90will be carried in the vicinity where a gap is formed as the endwall 34of slot 30 is separated from the leading or trailing edge of the movablecam member 42. In such embodiments, the length of the roller 90 in thelongitudinal direction of roller 90 must be longer than the width of camsurface 54 defined between edges 60 of movable cam member 42 so that inoperation, roller 90 extends beyond edges 60 and can be received andcarried by upper cam receiving surfaces 39, 41, 239, 241 of oppositelydisposed base circle arcuate sections 38, 40, 238, 240, respectively.

In alternative embodiments such as shown in FIGS. 5, 5a, 6, 10, and 11,the roller 90 need not extend beyond edges 60 of cam surface 54 and basecircle arcuate sections 38, 40, 238, 240 likewise need not be provided.However, in order to carry roller 90 across the gap formed betweenendwalls 34 of slot 30 and the edges 35 of the leading or trailing rampsand/or the peripheral edges of the respective front and back ears, andthus avoid the introduction of discontinuous movements in opening andclosing the valves, a ramp tongue 120 is provided with a roller carryingsurface 122 which has the same radius of curvature as base circle band36 of hollow shaft 22. The length of roller carrying surface 122measured in the direction of rotation of cam member 42 aboutlongitudinal axis 24 of hollow shaft 22 must be long enough to bridgethe gap formed between endwalls 34 of slot 30 and the peripheral edgesof the movable cam member opposed to the endwalls of the slot.

As shown in FIG. 9 for example, a hollow shaft 22 can be provided withbase circle arcuate sections 38, 40, 238, 240 and recess 118 so thatsuch hollow shaft could be used with an embodiment employing a rollerthat was longer than the width of a cam member or shorter than the widthof the cam member. Removal of base circle arcuate- sections 38, 40, 238,240 from the embodiment shown in FIG. 9 would yield an embodiment suchas shown in FIG. 5 for example.

What is claimed is:
 1. An actuating apparatus employing one or morecams, comprising:(a) an elongated hollow shaft, said shaft defining alongitudinal axis, an exterior surface, an interior surface, and a slotdefined through said interior and exterior surfaces,i) said interiorsurface of said hollow shaft defining an interior cylindrical bearingsurface, ii) said slot being defined by a pair of opposed sidewalls anda pair of opposed endwalls disposed between said sidewalls, each saidslot sidewall extending in a direction transverse to said longitudinalaxis, iii) said exterior surface of said hollow shaft further defining abase circle band having a constant radius of curvature and extendingcircumferentially between said endwalls of said slot, (b) a movable cammember, said movable cam member defining an actuating lobe and a seatingmember integrally connected to said actuating lobe,i) said actuatinglobe defining a cam surface, ii) said seating member defining an outercylindrical shaft bearing surface disposed opposite said cam surface,iii) said outer cylindrical shaft bearing surface being configured torotatably engage said interior cylindrical bearing surface of saidhollow shaft, iv) each of said actuating member and sad cam surfacehaving a width configured to project through said slot of said hollowshaft when said outer cylindrical shaft bearing surface is disposed torotatably engage said interior cylindrical bearing surface of sad hollowshaft, said width of said cam surface being defined by opposed edges, v)said cam surface being configured to engage the cam follower anddefining a nose portion, a leading ramp, and a trailing ramp, vi) saidnose portion being disposed between said leading ramp and said trailingramp, relative to said leading ramp and said trailing ramp said noseportion being the portion of said cam surface disposed the greatestdistance away from said outer cylindrical shaft bearing surface, vii)said leading ramp forming the portion of said cam surface that the camfollower engages before engaging said nose portion during revolution ofsaid hollow shaft about said longitudinal axis of said hollow shaft,viii) said trailing ramp forming the portion of said cam surface thatsaid follower engages after passing said nose portion during revolutionof said hollow shaft, ix) said nose portion of said cam surface beingformed by the outer surface of a circular cylindrical roller member, x)said roller member being rotatably mounted in said actuating lobebetween said leading ramp and said trailing ramp; (d) an elongated innershaft defining an axis of rotation along the length thereof and havingan outer surface; and (e) means for nonrotatably connecting sad innershaft and said movable cam member for simultaneous rotational movement.2. An apparatus as in claim 1, wherein:i) said exterior surface of saidhollow shaft defining a pair of recesses, each sad recess extending in adirection transverse to said longitudinal axis of said hollow shaft, oneend of one of said recesses communicating with one end of said slot, oneend of the other of said recesses communicating with the opposite end ofsaid slot, ii) one of said recesses being defined through one end ofsaid base circle band and the other of said recesses being definedthrough the opposite end of said base circle band; iii) said movable camfurther defining a pair ramp tongues, each of said ramp tongues definingan exterior roller carrying surface, each of said exterior rollercarrying surfaces being defined near its free end by the same radius ofcurvature that defines said base circle band of said hollow shaft, eachsaid exterior roller carrying surface of each said ramp tongue defininga width measured in the direction of said longitudinal axis of rotationof said movable cam member, each said width of each said exterior rollercarrying surface being narrower than said width of said cam surface, iv)one of said ramp tongues extending from the end of said leading rampdisposed opposite from said nose portion, and the other of said ramptongues extending from the end of said trailing disposed opposite fromsaid nose portion, ramp v) each said ramp tongue being long enough toextend beyond and across the maximum exposure of said adjacent portionof said slot in said hollow shaft when said outer cylindrical shaftbearing surface of said movable cam member is disposed to engage saidinterior cylindrical bearing surface of said hollow shaft and saidmovable cam member is displaced the maximum amount in a directionrotating away from said adjacent endwall of said slot, vi) each saidrecess of said exterior surface of said hollow shaft being configuredjust wide enough to receive one of said ramp tongues, and vii) each saidramp tongue being configured and disposed to be received into one ofsaid recesses when said outer cylindrical shaft bearing surface of saidmovable cam member is disposed to engage said interior cylindricalbearing surface of said hollow shaft.
 3. An apparatus as in claim 1,further comprising:(e) a cam follower, said cam follower including:i) atappet defining a circular cylindrically shaped surface for engagingsaid cam surface of said movable cam member, and ii) means for holdingsaid tappet surface at a fixed orientation relative to the path ofrotation of said movable cam member.
 4. An apparatus as in claim 3,wherein: said means for holding said tappet surface at a fixedorientation relative to the path of rotation of said movable cam memberincludes a key member and a groove for slidably receiving said keymember, said groove being configured to restrict movement of said keymember to one predetermined path, wherein only one of said key memberand sad groove are connected to said tappet.
 5. An apparatus as in claim1, further comprising:(e) a second cam member disposed adjacent saidmovable cam member, said second cam member having an identical camsurface profile to said movable cam member.
 6. An apparatus as in claim5, wherein: said second cam member is fixed to said exterior surface ofsaid hollow shaft adjacent one of said sidewalls of said slot.
 7. Anapparatus as in claim 6, wherein: said nose portion of said cam surfaceof said second cam member being formed by the outer surface of a secondcircular cylindrical roller member.
 8. An apparatus as in claim 5,further comprising:(f) a cam follower, said cam follower including:i) atappet defining a circular cylindrically shaped surface for engagingsaid cam surfaces of said movable cam member and said second cam member,and ii) means for holding said tappet surface at a fixed orientationrelative to the path of rotation of said movable cam member and saidsecond cam member.
 9. An apparatus as in claim 8, wherein: said meansfor holding said tappet surface at a fixed orientation relative to thepath of rotation of said movable cam member and said second cam memberincludes a key member and a groove for slidably receiving said keymember, said groove being configured to restrict movement of said keymember to one predetermined path, wherein only one of said key memberand said groove are connected to said tappet.
 10. An apparatus as inclaim 9, wherein: said one predetermined path of movement of said keymember defines a straight line.